head to head
Neither is meaningfully harder - they pose close to the same test. The widest gap is variance, and it is a single point.

Execution · Competitive PvP
Destructible-environment shooter with tight gunplay.

Execution · Competitive PvP
Cold War-era shooter pairing twitch multiplayer with the cult Zombies mode.
Battlefield: Bad Company 2 leans Execution (Competitive PvP); Call of Duty: Black Ops leans Execution (Competitive PvP).
Same score on execution - which means the number cannot separate them. The difference is in what each one asks of you.
Battlefield: Bad Company 2
Bullet drop and recoil demand real aim
Call of Duty: Black Ops
Gunfights hinge on aim and reaction speed
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Battlefield: Bad Company 2
Destruction and flanks punish positional reads
Call of Duty: Black Ops
Reading human opponents' positioning and timing
Call of Duty: Black Ops leans a little harder on variance, though the gap is small.
Battlefield: Bad Company 2
Some vehicle/spawn randomness, mostly skill
Call of Duty: Black Ops
Spawns, care packages, zombies RNG
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
Battlefield: Bad Company 2
Class kits and gadgets optimize objectives
Call of Duty: Black Ops
Class builds, map control, zombies routing
A matching score does not mean a matching test. Two games can both sit at 10 on execution and demand completely different things of you - which is why the reasoning above matters more than the number beside it.